The four white New York City police officers charged with murder for shooting down an unarmed black man in a hail of 41 bullets were acquitted today on all counts in a case that has become a rallying cry for racial justice.

A New York State Supreme Court jury of seven white men, one white woman and four black women deliberated for more than 20 hours over three days before deciding that the officers were justified in fatally shooting Amadou Diallo a year ago because they believed he had a handgun and would fire at them.

Diallo, a 22-year-old immigrant from Guinea who worked as a street vendor and hoped to attend an American college, died after being hit by gunfire 19 times.

The officers--Edward McMellon, 27; Sean Carroll, 37; Kenneth Boss, 28; and Richard Murphy, 27--wept as the "not guilty" verdict was repeated 24 times, with each officer facing six charges ranging from second-degree intentional murder of Diallo to reckless endangerment of bystanders. Carroll, who along with McMellon emptied his 16-round clip in the shooting, fingered rosary beads while families of the officers held each other and wept.

Across the aisle of the ornate white and gold-painted courtroom, Diallo's mother, Kadiatou Diallo, held her head high as tears streamed down her cheeks. Along with her husband, Saikou Diallo, she has lived in the United States since her son's death and had spearheaded a movement to bring the officers to justice.

New York State Supreme Court Justice Joseph Teresi, who presided over the trial, said after the jury announced the verdict that "the book is closed" on the case.

But Mary Jo White, the U.S. attorney for the Southern District of New York, said the Justice Department's Civil Rights Division will review the case to see whether there were any violations of the federal criminal civil rights laws. Such review routinely follows the acquittal in state court of police officers who are accused of violating a person's rights. Diallo's parents also plan a civil suit.

Outside the courthouse in Albany, where the trial was moved from the Bronx at the request of defense attorneys, Diallo's mother stood in a driving rain in front of a wall of broadcast cameras and thanked supporters. "It's in the name of Amadou and his spirit that I ask for your calm and prayers," she said.

Jurors refused to discuss their verdicts and were escorted by police from the courthouse. But from the legal instructions that guided their deliberations it was clear that they found the officers' actions reasonable under the circumstances.

Defense attorney Stephen Worth said the officers' testimony made the difference in the case. "What they had to say is the truth," Worth said. "Their reaction, obviously, they're relieved. We all recognize the fact that someone died. Amadou Diallo died. That's always remembered. But they're relieved.

"The point is the police officers have to be able to do their job and do it the right way," Worth said.

Bennett Epstein, another defense attorney, accused prosecutors of bringing charges against the four officers in response to "mob justice" in New York City, where Diallo's death sparked a deep outcry last year and weeks of daily protests. "Now is the time for healing, and we must never let this happen again," he said.

But as Epstein and the other defense attorneys departed microphones set up in the barricaded streets, a protester shouted, "You better watch your back! You better watch your back. Your clients are murderers."

Al Sharpton, the civil rights activist who has been the Diallo family's spokesman, repeated the call for calm before departing Albany tonight for New York City.

"We come tonight first saying that this not the end, this is only the beginning," Sharpton said here. "We said from the beginning that we would pursue this to the federal courts."

Numerous activists and politicians criticized the change of venue to Albany as a slap at the judgment of minorities in the Bronx. African Americans are 9 percent of Albany's population but 38 percent in the Bronx.

Legal experts viewed the move to Upstate New York as key for the defense. The case had not assumed the massive symbolic proportions here in Albany that it had in the Bronx, and jurors here are generally considered more sympathetic to police.

Because Diallo was unarmed and simply standing in front of his building at the time of his encounter with police, civil rights activists seized upon the case as an example of what they say is a police department that without reason stops and frisks thousands of people, mostly African Americans and Latinos, as part of Mayor Rudolph W. Giuliani's effort to curb crime. The practice has been harshly criticized because only a small percentage of such encounters actually results in arrests.

On the night of the deadly encounter with Diallo, the four officers--members of an elite street crimes unit--were looking for an armed rapist who had struck repeatedly in the Bronx. When they saw Diallo standing on the stoop of his building, they suspected he might have been acting as a lookout for a robbery. They believed, the officers testified, that Diallo was armed because he pulled a black object from his pocket when they approached him. It turned out to be his wallet.

In nine days of testimony, including the first public statements on the slaying by the four officers themselves, defense attorneys sought to show that the officers reasonably believed Diallo had a gun; that he would fire on them; that he ignored the officers' commands to show his hands; and that he held the suspected gun in a threatening manner as the officers converged on him in a vestibule that the officers said was dimly lit.

Defense attorneys called the only expert witness on police procedure during the trial, James Fyfe, a Temple University criminologist. His testimony supported the officers' actions. The prosecution did not cross-examine Fyfe and did not call any of its own experts to rebut his opinions.

Eric Warner, the lead prosecutor from the Bronx district attorney's office, argued that it was unreasonable for the officers to believe that Diallo posed a threat to them. In closing statements, Warner argued that the officers prejudged Diallo from the moment they saw him from a distance and that the prejudgment that he was a criminal suspect doomed him to death. Warner argued that the officers themselves caused their encounter with Diallo to escalate to the point of a fusillade of unjustified gunfire.

The jury appeared to deliberate methodically. Jurors requested all of the officers' testimony to be read back to them, as well as Fyfe's testimony and that of Schrrie Elliot. Elliot, a neighbor of Diallo who was the only non-police eyewitness, testified that police had pulled up upon Diallo, alighted from their car with guns drawn and formed a semicircle on the sidewalk below the stoop where Diallo stood. This contradicted the testimony of the officers, who said they only drew their guns when Diallo refused their orders.

Diallo's mother said she had nothing to say to the officers but that "the race issue should be addressed. Racial profiling has to stop in every neighborhood."

"I'm not sure my son knew he was killed by police," Diallo's mother told CNN's "Larry King Live" tonight, describing his encounter with four men "without uniforms, in the middle of the night who got out of their car and just approached him."

Staff writer Lorraine Adams contributed to this report.